Often times one of the pigs is unable to cross the ramp from the dining room to the bed room because of another pig. But it's usually because they're standing right there in the way being grouchy, and running over the ramp would incite a fight. All three of the pigs have been in this situation.
But one time it really seemed like Fuzzy was blocking Potato on purpose. Especially when he closed the ramp on him! That was uncharacteristically clever for Fuzz-Ball.